In cellular wireless networks, base stations and user equipments (UE) are communicated with each other by utilizing two transmission direction, downlink (DL) and uplink (UL), respectively, and above-said communication is also known as a uplink-downlink (UL-DL) communication. In addition, a specific application protocol may also be used between base stations 110 to 150, so as to solve problems of mutual interference, management of the UE and so forth.
During reconfiguration of a base station adopting 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Time-Division Duplexing (TDD), a corresponding UL-DL standard configuration may be selected according to current UL-DL transmission conditions, such as UL traffic and DL traffic, to improve transmission traffic. In a LTE TDD standard, a plurality of UL-DL standard configurations are provided.
Referring to FIG. 1 and Table (1), FIG. 1 is a schematic diagram of a wireless communication system. In FIG. 1, with reference to related settings as shown in Table (1), each of cell stations 110 to 150 selects one UL-DL configuration according to the UL-DL transmission conditions on their own. Table (1) discloses seven configurations among the UL-DL standard configurations in 3GPP Long Term Evolution (LTE) TDD. Each of the UL-DL standard configurations uses one frame as a unit, and each frame has 10 subframes.
TABLE 1DL-ULSwitch-UL-DLPointCellConfig-Period-Subframe NumberStationurationicity012345678911005 msDSUUUDSUUU14015 msDSUUDDSUUD25 msDSUDDDSUDD120310 ms DSUUUDDDDD410 ms DSUUDDDDDD150510 ms DSUDDDDDDD13065 msDSUUUDSUUD
Each of the cell stations 110 to 150 selects the corresponding UL-DL configuration according to the UL-DL transmission condition of their own. For instance, the cell stations 110, 120, 130, 140, 150 select the UL-DL configurations 0, 3, 6, 1 and 5, respectively. A base station communication link may also be provided between the cell stations, such as base station communication links 102, 104, 106 provided between the base stations 110 and 120, between the base stations 120 and 130, and between the base stations 140 and 150, respectively. Table (1) illustrates information for each of the configurations, in which “DL-to-UL Switch-point Periodicity” is 5 ms or 10 ms, and configurations for the subframes 0 to 9 are as shown in Table (1). In Table (1), “D” refers to the subframe for a DL transmission, “S” refers to one special subframe for a guard time; and “U” refers to the subframe for a UL transmission.
When the cell station 120 adopting the UL-DL configuration “3” transmits a DL 101 in the subframes 7 and 8, it may cause a severe interference to a neighboring cell station 110 adopting the UL-DL configuration “0” to receive the subframes 7 and 8 in a UL 103. This is because a transmission power of the cell station 120 for DL 101 is far greater than the cell station 120 of a user equipment UE in transmitting the UL 103. In case the user equipment UE and a neighboring picocell base station are transmitting at the same time but with different configurations, a UL Signal-to-interference noise ratio (SINR) of the user equipment UE is interfered by the DL of the picocell base station more seriously. Therefore, how to mitigate interferences between the base stations is a major issue in the field of LTE TDD wireless network technology.
Moreover, base station information for communication between a plurality of Evolved Node Base stations (eNBs) plays a very important role in the interference management method. Accordingly, the interference management method based on base station information exchange is currently under development.